A valve with an actuator of this kind is already known, comprising a device capable of detecting that the actuator is operating the valve. This device may consist of electrical limit contacts or a potentiometer which determines the position of the valve.
A valve of this kind has the following drawbacks. If the energy source is defective and is incapable of supplying the power required, the actuator will not be in a position to operate the valve. In numerous installations in which the valve has a safety function and must operate without fail at a given moment, one would wish to be certain that at that instant the energy source is capable of supplying the necessary power and consequently would want to be able to check in advance that it is indeed capable of operation and to be warned if it is not. Nor is there any warning as to the condition of the valve or its degree of wear. If a foreign body is obstructing the operation of the valve, there is no way of knowing this either.